Scientists from USDA’s Agricultural Research Service (ARS) are taking a sideways look at odors, literally.

As anyone that has evaluated potential sites for swine facilities knows, many factors–such as wind speed, direction, topography, vegetation, and more–influence the potential impacts on downwind neighbors. In an effort to understand how air currents interact with the building site–and therefore pick up odors, dust, and other emissions–Tom Sauer and Jerry Hatfield, with the National Soil Tilth Laboratory in Ames, Iowa, built a model swine farm in a wind tunnel.

Research Activities

Air flow velocities and turbulence intensities were measured with a sensor that measured how quickly the winds carried heat away at 83 points behind the building models. They also took pictures of smoke patterns, generated by dry ice, to capture airflow patterns around the model structures and measured evaporation rates from the model storage tanks and lagoons. They reconfigured the model farm in different ways and repeated their measurements.

What Did They Learn?

Buildings situated perpendicular to airflow disrupted downwind airflow to a greater extent than buildings parallel to airflow. “These studies show how much the placement of animal housing units and manure-storage facilities can work in combination with prevailing winds and site conditions to affect the distance that potential agricultural air emissions can travel,” says Sauer. “They strongly indicate that we should be able to reduce the downwind air-quality impacts from animal production by modifying the layout of a production facility.”

Using model farm buildings, silos, and trees (wire mesh coils serve as trees), agronomist Guillermo Hernandez (left) and soil scientist Tom Sauer evaluate the effect of model arrangements on airflow. Hernandez makes an adjustment to one of the highly sensitive probes as Sauer monitors the real-time data signal. Photo courtesy of the USDA Ag Research Service.

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This is a national Cooperative Extension resource

This work is supported by New Technologies for Agriculture Extension grant no. 2015-41595-24254 from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.